BACKGROUND
Surface plasmons (SP) and surface plasmon polaritons (SPP) are nonlinear 36 many-body excitations that couple light with the electron density of states of a material, in 37 particulars, metals. The nonlinear nature of SP and SPP can be used for frequency doubling of 38 light (second harmonic generation) and the formation of evanescent waves that enhance 39 the Raman signature of molecules on a surface (surface enhanced Raman spectroscopy), to 40 name a few. More recently, plasmonics are being utilized in metalenses, a two-dimensional lens 41 that mitigates aberrations and stigmatisms associated with traditional 3D lenses. The future 42 of metalens technology rests on the shoulders of the materials science community to develop 43 new plasmonic materials that have a broader suite of capabilities and superior nonlinear 44 responses.
SUMMARY OF TECHNOLOGY
Novel Au meso-structures with a polyhedron shape, henceforth referred to as 17 pyramids, are produced by annealing in vacuo an Au thin film on a Si(100) substrate. Gold 18 diffusion and incorporation into pyramids is a function of the thickness of the Au film, the 19-annealing temperature, and vacuum pressure. The Au pyramids have unique surface 20 morphologies due to the presence of channels and plateaus, where channels are cut into the 21 surfaces of the pyramids and plateaus are the surfaces between adjacent channels. The bulk of the 22 pyramids consists of Au with cavities that are devoid of Au or Si. Normalized Energy dispersive 23 spectroscopy (EDS) of intact regions of the surface are 98.1 wt% Au and 1.9 wt% Si, while the 24 bottoms of the channels are 85.7% wt% Au and 14.3 wt% Si. Therefore, one step in the growth 25 process is the formation of an Au-Si eutectic. The low concentration of Si in the solid regions of 26 the pyramid and its high concentration in the walls of the cavities are indicative of phase 27 separation of the Au-Si eutectic. The pyramids are oriented in the same direction relative to one 28 another and is a consequence of eutectic formation induced etching of the Si (100) surface. The 29-scattering spectrum (non-specular reflectivity) of the Au pyramids consists of two very strong 30 surface plasmon polaritons states that correspond to excitation from the Au d-bands to the sp 31 conduction bands. The surface morphology produces linearly polarized reflected light.
POTENTIAL AREAS OF APPLICATION
MAIN ADVANTAGES
STAGE OF DEVELOPMENT